The rewind area is really an excellent idea! And like @Fabio Alessandro Locati said, the Play/Pause button should be moved to any corner IMO. In Android for example is extremely annoying when you tap the play and the control continues to show on screen while you try to see the video.

the speed with which the rewind/fastforward happens could be determined by how far above the user's finger is from the bottom of the screen. farther above = faster scrubbing.. this is similar to the scrubbing in iOS.